The conventional layered heat exchangers for use as layered evaporators for motor vehicle air conditioners include two types; one wherein headers are provided at one of the upper and lower sides of the exchanger, and the other wherein headers are provided at both of the upper and lower sides.
Conventional heat exchangers comprise, for example, intermediate plates each provided in one side thereof with a tube forming recessed portion and header forming recessed portions having a larger depth than this portion and continuous with at least one of the upper and lower sides thereof. Each of the header forming recessed portions has a fluid passage hole formed in its bottom wall. The intermediate plates are fitted together in juxtaposed layers, with the recessed portions of each plate opposed to the corresponding recessed portions of the plate immediately adjacent thereto to thereby provide juxtaposed flat tubes and headers in communication with the flat tubes. An end plate is provided at each of the left and right sides of the plate arrangement externally thereof.
With the layered heat exchanger described above, it is important to distribute a fluid from the header to the flat tubes uniformly. Uniformly divided flows of the fluid are formed, for example, by adjusting the number of flat tubes. However, this method encounters the problem of failing to divide the fluid fully uniformly or attaining uniform division of the fluid at the sacrifice of channel resistance to the fluid.
For this reason, the problem of an insufficient cooling efficiency arises when such a layered heat exchanger is used as the evaporator for motor vehicle air conditioners. Further in the case where such a layered heat exchanger is used as the evaporator to provide a refrigeration system which comprises a compressor for compressing a refrigerant, a condenser for condensing the compressed refrigerant, a pressure reducing device for passing the condensed refrigerant therethrough for a pressure reduction, and an evaporator for evaporating the refrigerant from the device to return the resulting refrigerant to the compressor, the refrigeration system has the problem of being insufficient in overall efficiency since the evaporator is insufficient in the function of diffusing the refrigerant therethrough.
An object of the present invention is to provide a layered heat exchanger wherein the refrigerant can be allowed to flow out of the header into flat tubes in uniformly divided streams.
Another object of the present invention is to provide a layered evaporator for motor vehicle air conditioners wherein the refrigerant can be allowed to flow out of the header into flat tubes in uniformly divided streams and which is therefore improved in cooling efficiency.
Another object of the invention is to provide a refrigeration system which is improved in overall efficiency by incorporating therein a layered heat exchanger wherein the refrigerant can be allowed to flow out of the header into flat tubes in uniformly divided streams.